[BUG] Pod restart of etcd-0 after scale-up failed with panic

[ishan16696]

Describe the bug:
While testing the scale-up feature I observed that after other 2 pods starts running fine, 0th pod goes to CrashLoopBackOff due to panic in its etcd container. And backup-restore didn’t detect any db corruption.

Expected behavior:
If data corruption occurs then backup-restore should be able to detect the db corruption and should have taken required action.

How To Reproduce (as minimally and precisely as possible):

1. Do scale-up of etcd cluster from .spec.replicas=1 to .spec.replicas=3
2. try many times, you might see 2 other members join the cluster but

etcd-main-0                   1/2     CrashLoopBackOff   19 (2m24s ago)   75m
etcd-main-1                   2/2     Running            0                88m
etcd-main-2                   2/2     Running            2 (88m ago)      88m

Backup-restore Logs:

time="2023-05-02T09:28:42Z" level=info msg="Validation mode: full" actor=backup-restore-server
time="2023-05-02T09:28:42Z" level=info msg="Responding to status request with: Progress" actor=backup-restore-server
time="2023-05-02T09:28:42Z" level=info msg="Checking whether etcd cluster is marked for scale-up" actor=member-add
time="2023-05-02T09:28:42Z" level=info msg="Checking if member etcd-main-0 is part of a running cluster" actor=member-add
time="2023-05-02T09:28:42Z" level=info msg="Member etcd-main-0 part of running cluster" actor=member-add
time="2023-05-02T09:28:42Z" level=info msg="Checking for data directory structure validity..."
time="2023-05-02T09:28:42Z" level=info msg="Checking for Etcd revision..."
time="2023-05-02T09:28:42Z" level=info msg="Skipping check for revision consistency of etcd member as it will get in sync with etcd leader."
time="2023-05-02T09:28:42Z" level=info msg="Checking for data directory files corruption..."
time="2023-05-02T09:28:42Z" level=info msg="Verifying snap directory..."
time="2023-05-02T09:28:42Z" level=info msg="Verifying WAL directory..."
time="2023-05-02T09:28:42Z" level=info msg="Verifying DB file..."
time="2023-05-02T09:28:42Z" level=info msg="Data directory valid."
time="2023-05-02T09:28:42Z" level=info msg="Successfully initialized data directory for etcd." actor=backup-restore-server
time="2023-05-02T09:28:43Z" level=info msg="Responding to status request with: Successful" actor=backup-restore-server
time="2023-05-02T09:28:43Z" level=info msg="Updating status from Successful to New" actor=backup-restore-server
time="2023-05-02T09:28:43Z" level=info msg="checking the presence of a learner in a cluster..." actor=member-add
time="2023-05-02T09:28:43Z" level=info msg="Served config for ETCD instance." actor=backup-restore-server

Etcd Logs:

2023-05-02 09:33:48.983240 I | etcdserver: restarting member a789d1ab8da2e800 in cluster ffa0021a34a4dfd7 at commit index 0
raft2023/05/02 09:33:48 INFO: a789d1ab8da2e800 switched to configuration voters=()
raft2023/05/02 09:33:48 INFO: a789d1ab8da2e800 became follower at term 0
raft2023/05/02 09:33:48 INFO: newRaft a789d1ab8da2e800 [peers: [], term: 0, commit: 0, applied: 0, lastindex: 0, lastterm: 0]
2023-05-02 09:33:48.986153 W | auth: simple token is not cryptographically signed
2023-05-02 09:33:48.988626 I | etcdserver: starting server... [version: 3.4.13, cluster version: to_be_decided]
2023-05-02 09:33:48.991139 I | embed: listening for peers on [::]:2380
2023-05-02 09:33:49.052926 I | rafthttp: started HTTP pipelining with peer a9dfaad6ed1426aa
2023-05-02 09:33:49.052991 E | rafthttp: failed to find member a9dfaad6ed1426aa in cluster ffa0021a34a4dfd7
2023-05-02 09:33:49.053298 E | rafthttp: failed to find member a9dfaad6ed1426aa in cluster ffa0021a34a4dfd7
2023-05-02 09:33:49.056043 I | rafthttp: started HTTP pipelining with peer 2d3b31aaf470abd0
2023-05-02 09:33:49.056102 E | rafthttp: failed to find member 2d3b31aaf470abd0 in cluster ffa0021a34a4dfd7
2023-05-02 09:33:49.056381 E | rafthttp: failed to find member 2d3b31aaf470abd0 in cluster ffa0021a34a4dfd7
raft2023/05/02 09:33:49 INFO: a789d1ab8da2e800 [term: 0] received a MsgHeartbeat message with higher term from a9dfaad6ed1426aa [term: 3]
raft2023/05/02 09:33:49 INFO: a789d1ab8da2e800 became follower at term 3
raft2023/05/02 09:33:49 tocommit(22) is out of range [lastIndex(0)]. Was the raft log corrupted, truncated, or lost?
panic: tocommit(22) is out of range [lastIndex(0)]. Was the raft log corrupted, truncated, or lost?

goroutine 125 [running]:
log.(*Logger).Panicf(0xc0001318b0, 0x10db3a0, 0x5d, 0xc000546260, 0x2, 0x2)
	/usr/local/go/src/log/log.go:219 +0xc1
go.etcd.io/etcd/raft.(*DefaultLogger).Panicf(0x1ac1310, 0x10db3a0, 0x5d, 0xc000546260, 0x2, 0x2)
	/tmp/etcd-release-3.4.13/etcd/release/etcd/raft/logger.go:127 +0x60
go.etcd.io/etcd/raft.(*raftLog).commitTo(0xc00024d110, 0x16)
	/tmp/etcd-release-3.4.13/etcd/release/etcd/raft/log.go:203 +0x131
go.etcd.io/etcd/raft.(*raft).handleHeartbeat(0xc0001b9540, 0x8, 0xa789d1ab8da2e800, 0xa9dfaad6ed1426aa, 0x3, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	/tmp/etcd-release-3.4.13/etcd/release/etcd/raft/raft.go:1396 +0x54
go.etcd.io/etcd/raft.stepFollower(0xc0001b9540, 0x8, 0xa789d1ab8da2e800, 0xa9dfaad6ed1426aa, 0x3, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	/tmp/etcd-release-3.4.13/etcd/release/etcd/raft/raft.go:1341 +0x480
go.etcd.io/etcd/raft.(*raft).Step(0xc0001b9540, 0x8, 0xa789d1ab8da2e800, 0xa9dfaad6ed1426aa, 0x3, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	/tmp/etcd-release-3.4.13/etcd/release/etcd/raft/raft.go:984 +0x1113
go.etcd.io/etcd/raft.(*node).run(0xc00007faa0)
	/tmp/etcd-release-3.4.13/etcd/release/etcd/raft/node.go:352 +0xab6
created by go.etcd.io/etcd/raft.RestartNode
	/tmp/etcd-release-3.4.13/etcd/release/etcd/raft/node.go:240 +0x33c

Answer we need to know to find-out?:
It should be simple pod restart, why kind of corruption occurs ? what etcd was expecting, so why it got panic if its not corruption ?
Why it happens after scaling up and other 2 members joins ?